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Topic: Ions and electrodes  (Read 2254 times)

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Offline iScience

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Ions and electrodes
« on: September 13, 2013, 07:38:00 PM »
when i was in general chemistry being introduced to electrochemical cells, the metal atoms existed as an ion only in their aqueous state and was not allowed to exist as an ion when adsorbed onto the solid metal chunk (electrode) why? is this because once the metal adsorbs onto the solid its wave function no longer is an independent one and therefore its energy level fuses with the conduction band of the electrode thereby distributing what charge it had to the rest of the electrode?
« Last Edit: September 14, 2013, 04:59:47 AM by Dan »

Offline 408

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Re: Ions and electrodes
« Reply #1 on: September 14, 2013, 01:24:47 PM »
I would avoid thinking of this in terms of wave functions. 

First, chemical systems prefer the most stable state.  A micelle develops such that the hydrophobic parts are inside, and the hydrophillic face out towards the aqueous solution.

When you consider a metal, you have complete fluidity of electrons.  When a metal is oxidized it makes sense that the cationic species end up on the exterior of the electrode as the positive charges interact nicely with the partial negative charges of the water molecules.  But as the redox continues, what happens?  more postitive charged species are created which also prefer the aqueous boundary of the electrode.  These repel each other easily making for solvation with the help of the water present.  But it is entirely possible that as a transient effect that, yes there are surface ions.

Consider a gold surface interacting with thiols.  In the bulk gold of course the oxidation state is zero.  But each gold atom bound to a thiol is formally +1 charged.

Offline blaisem

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Re: Ions and electrodes
« Reply #2 on: September 18, 2013, 04:57:45 PM »
In general, ions are soluble in polar solutions because the solvent molecules typically have intramolecular dipole moments.  The most common example is water, which has a positive dipole on the hydrogen atoms and a negative dipole on the oxygen, due to Oxygen's greater electronegativity.  This means that, when an ion enters solution, it is immediately surrounded by its counterpart charge from the dipoles of the solvent molecules.  This is termed solvation.  When the solute is ions, the solution is called electrolytic.  Solvated ions are in the aqueous state.

Regarding your question, what type of interaction occurs between the cations and electrons at the cathode?

Given my paragraph above, will the cation still be soluble after this interaction?
« Last Edit: September 18, 2013, 05:10:59 PM by blaisem »

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